maker sure the meta packages are not forced of the system by breaks/conflicts of their dependencies

currently apt will happily remove librem5-gnome and phoc because e.g. librem5-devkit-base has a conflicts on a specific phoc version. We rather want apt to do nothing in this case. This could be fixed by making the meta packages essential but maybe there's a smaller hammer? @matthias.klumpp , @jonas.smedegaard you maybe have another idea?